The linear alternating polymers of carbon monoxide and styrene are known in the art from the disclosures of U.S. Pat. No. 4,788,279, being produced in the presence of a catalyst composition formed from a palladium compound, the anion of a non-hydrohalogenic acid having a pKa less than 2, a bidentate ligand of nitrogen and an organic oxidant. In terms of the fine structure of such linear alternating polymers, they are termed regioregular and syndiotactic, having an average syndiotacticity of from about 60% to about 85% depending in part upon the particular catalyst composition and reaction conditions selected for the polymerization.
The term "regioregular" as applied to the carbon monoxide/styrene copolymers refers to the manner in which the moieties derived from styrene are bound chemically to the moieties derived from carbon monoxide. If the styrene moieties are connected to the carbon monoxide moieties in predominantly a head-to-tail fashion, the polymer is termed regioregular. A polymer with less than a predominance of head-to-tail bonding is termed regio-irregular or non-regioregular. The term "syndiotactic" refers to the configuration of the asymmetric carbon atoms in the linear alternating polymer. When the configuration of the asymmetric carbon atoms is the same, e.g., ##STR1## wherein the wavy lines indicate the continuing polymer chain, the polymer is termed isotactic. However, when the configuration of adjacent asymmetric carbon atoms is opposite, e.g., ##STR2## the polymer is termed syndiotactic. A polymer in which there is no predominant or regular arrangement of adjacent asymmetric carbon atoms is termed atactic or stereo-irregular.
In practice, however, any given polymer will not be completely structured in either of the isotactic or syndiotactic forms. If more than 50% of the adjacent asymmetric carbon atoms are oppositely configured relative to the adjacent asymmetric carbon atom, the polymer is considered to be syndiotactic. The average percentage of such carbon atoms of syndiotactic configuration is termed the average syndiotacticity. The production of atactic linear alternating polymers of carbon monoxide and styrene is disclosed in copending U.S. patent application Ser. No. 352,235, filed May 15, 1989, now U.S. Pat. No. 4,965,341.
For some applications it is desirable to have a linear alternating copolymer of carbon monoxide and styrene which has a high degree of syndiotactic character, i.e., the polymer would be highly syndiotactic. For other applications, an atactic polymer is preferred. It would be of advantage to provide a method for reducing the syndiotactic character of a linear alternating carbon monoxide/styrene copolymer and at the same time increase the atactic character of the resulting polymer.